The actor met 27-year-old Sally Russell who died a few days before The Magic Of Words was published last month.
Sally lived in Glasgow and was originally from Dornoch in the Highlands. She had a double lung transplant in 2011 but shortly after graduating with first-class honours from Glasgow University she became dependent on oxygen.
Her grandfather, the Very Rev Dr James Simpson, wrote the book and is a former Moderator of the General Assembly of the Church of Scotland, a post once held by Tennant’s father, the Very Rev Sandy McDonald.
Tennant visited the Glasgow University graduate in hospital shortly before she died on October 21.
In a message written for the book launch, he said: “I remember with love and affection my meeting with Sally who has now sadly passed away after her courageous fight with cystic fibrosis.
“I honour your huge financial contribution to research into cystic fibrosis.”
Dr Simpson has written more than a dozen books and topped the bestseller list in Scotland for three months with Holy Wit.
The Magic Of Words is a humorous collection of stories and anecdotes with all proceeds from the sale of the book going towards research into the disease.